Tagging photos of my deceased father, name displayed when hover over photo is my living brother?

Typically this happens if you create a tag that is not connected to anyone in the Tree (in this case, a tag named "Hans Adolph Hafen") and then later connect it to someone else in the tree (In this case Arlo John Hafen KWCR-Y6Q). Then you have a tag with one name (which is what is shown when you hover over the tag in the memory viewer) that is connected to a person in the Tree with a different name (which is shown in the list of Tagged People on the right).

Regardless of how this came to be, the fix is the same:

1. Go to a photo that has a tag with this problem.
2. In the list of Tagged People, find the problematic tag, and click the gear icon to the right of the name.
3. That will pop up a little dialog box that contains the Tag Name, which will be underlined to indicate you can click on it. Click on it.
4. In the screen that appears, you will see "Hans Adoph Hafen" in large letters. Click on it.
5. In the edit box that appears, replace the current value with the desired value "Arlo John Hafen", then click Save.
6. Click your browser's Back button to return to the photo. Now when you hover over the tag, it should show "Arlo John Hafen".

Being aware that the tag name in step 4 is clickable and editable is the key to fixing such problems, but it is not at all obvious from the user interface, so many people are not aware of this possibility.

As for your additional note about the memories counter showing 0, that has been reported multiple times. See Many Memories, but tab shows Zero